Electrodeless plasma lamps may be used to provide bright, white light sources. Because electrodes are not used, they may have longer useful lifetimes than other lamps. In many applications, it is desirable to have a lamp capable of high light collection efficiency. Collection efficiency can be expressed as the percentage of light that can be collected from a source into a given etendue, compared to the total light emitted by that source. High collection efficiency means that most of the power consumed by the lamp is going toward delivering light where it needs to be. In microwave energized electrodeless plasma lamps, the need for high collection efficiency is elevated due to the losses incurred by converting d.c. power to RF power. In many applications, it is also desirable to have a lamp with high luminous efficiency. Luminous efficiency can be expressed as lumens output per watt of input power to the lamp.